\nYou'd think that if there was major news about birth control, your gyno would tell you, right? Unfortunately, when it comes to contraception, chances are your doc is probably holding back a lot of key info. Why? She may assume that if you're not asking questions, you have all the details you need. More likely, her schedule is so slammed, she barely has time to check your vitals and do a perfunctory Pap. In fact, according to a recent Cosmo Web poll of more than 2,000 women, 33 percent of respondents said their gyno seemed rushed during their annual exam.
But what you don't know can hurt you. A recent study in the journal Human Reproduction found that two-thirds of unplanned pregnancies occur among women who use birth control but either utilized it incorrectly or were using methods that didn't mesh with their lifestyles. Plus, there are some reasons your method may not be as reliable at preventing pregnancy or protecting against STDs as you think it is. To be certain your birth control has you covered, read the scoop on seven not-so-well-known facts that could have a serious impact on your life.

Secret #1Your weight matters
According to a recent study published in Obstetrics and Gynecology, women age 18 to 39 who weigh 155 pounds or more are 60 percent more likely to have their birth-control pills fail, especially if they are on a low-estrogen variety. And since the average weight of American women is 152 pounds, according to the Centers for Disease Control and Prevention, this could happen to a lot of people. "Women who weigh more have a faster metabolic rate, which means they may need higher levels of hormones to prevent pregnancy," explains study author Victoria L. Holt, Ph.D., professor of epidemiology at the University of Washington. "Another possibility is that birth-control pills, which are fat soluble, stay in the women's fat stores, so they are not where they need to be -- in the bloodstream -- in order to work."

Holt adds that similar risks may exist with other hormonal methods, such as the Ortho-Evra patch (more on this later). If you weigh 155 pounds or more you should talk to your health-care provider about using a different method, such as the IUD, or combining the Pill with condoms for extra protection.

Secret #2One of the oldies is a goodie
There's a pregnancy-preventing option out there that is highly effective and you never have to think about...but nobody's telling you about it. Curious? It's the IUD (intrauterine device). IUDs are tiny T-shaped contraptions made out of a flexible plastic that a doc inserts into your uterus. Today's devices are perfectly safe, but there was one faulty brand, the Dalkon Shield, which was pulled off the market in the 1970s and gave the IUD a bad rap. Although they're very popular in many other countries, less than 1 percent of U.S. women use IUDs.

And that's too bad because an IUD is a great option for a young woman in a monogamous relationship (since the device doesn't protect against STDs). Once inserted, you can forget about it; it doesn't have any of the Pill's hormonal side effects; and it has one of the highest effectiveness rates of any contraceptive: Only one out of every 100 women with an IUD becomes pregnant per year. There are two types of IUDs: The newest one, called Mirena, delivers progestin into the uterine lining, which thickens the cervical mucus to prevent sperm from reaching your uterus and can be left in for up to five years, according to Michael Momtaz, an OB/GYN in New York City. The other type of IUD, ParaGard, is made with copper. It reduces sperm's ability to swim, prevents implantation of a fertilized egg and can be left in for up to 10 years. Your fertility returns to normal right after IUD removal.

The only drawbacks: Insertion can be slightly painful, spotting for the first few months afterward is common and you may experience slightly increased cramping during menstruation. Also, women with a history of pelvic inflammatory disease are not candidates for the IUD. Because the IUD could exacerbate the effects of a bacterial infection such as chlamydia, use one only if you're in a monogamous relationship with someone who's STD-free. The total cost of the device and insertion is between $350 and $550, which may be covered by your insurance.

Secret #3Certain condoms could be bad for you
The spermicide nonoxynol-9 -- which many condoms are coated with -- not only doesn't guard against STDs, as some people assume, but also may increase your risk of contracting HIV and other sexually transmitted infections. "Spermicides prevent pregnancy by damaging sperms' cell membranes, but in the process, they can also break down the protective outer layers of cells that line the vagina," explains David Grimes, M.D., vice president of biomedical affairs at Family Health International. The FDA believes that by damaging these cells, nonoxynol-9 may increase the risk of STD infection, and they are now considering putting warning labels on any products that contain spermicide, which includes contraceptive vaginal creams, certain condoms and the Today Sponge, which is expected to be back on drugstore shelves sometime this year.

Secret #4 When you start the Pill, you don't have to wait a whole month for pregnancy protection to kick in, and you don't have to start on a Sunday
Forget what you may have been told: "The magic number is seven days," says Dr. Grimes. After taking the Pill for just one week, during which you should use a backup method such as condoms, the hormones will be effective in blocking ovulation, and then you're good to get busy without the love glove (as long as you and your man are STD-free, of course).
And despite what your Pill instructions may say, you can start a pack on any day of the week. "There's no medical reason for a Sunday start," says Bryna Harwood, assistant professor of OB/GYN who specializes in family planning at the University of Pittsburgh. "That instruction was designed so women would not have a period on the weekend."

If you're already on the Pill and want to change your start date, here's how to make the switch: Next time you're on the placebo pills in the pack, which trigger menstruation, don't wait until Sunday to start a new pack; begin taking the next set of active pills early -- on whichever day of the week you want.

Secret #5You have hormonal options other than the Pill
There are two new methods on the market that work the same way as oral contraceptives but may be a safer bet since you don't have to remember them every day: the Ortho-Evra patch and the NuvaRing. Ortho-Evra is an adhesive patch (about an inch and a half across) that you wear for three weeks a month on your butt, abdomen, torso or upper arm and that delivers ovulation-preventing hormones through your skin. The patches cost between $35 and $60 each. NuvaRing is a flexible ring, also containing ovulation-stopping hormones, which you insert into your vagina and leave there for three weeks, then remove for one week, which causes you to have your period. The potential downside: Some ring users experience increased vaginal discharge and irritation. It costs $30 to $40 per month. If used correctly, both the patch and NuvaRing are 99 percent effective.

Secret #6Your chances of becoming pregnant while using birth control are higher than you might think
When a doctor tells you how effective the Pill or condoms are, he or she is probably citing its "perfect use" stats -- meaning its efficacy when used consistently and correctly each and every single time in research conditions. For the Pill, that number is an impressive 99 percent (meaning that over the course of a year, fewer than 1 woman in 100 on the Pill will become pregnant) and for condoms it's 97 percent. However, the effectiveness rate for typical use of the Pill (i.e., how it's used in real life), is about 94 percent, and it's only 86 percent for condoms.
To make the Pill as effective as possible, take it at the same time every day. To help you remember, try timing it with a daily activity, such as brushing your teeth in the morning. If you forget one or more pills, read the relevant instructions on the package and follow them exactly to avoid conceiving. Condoms are most reliable when they are used with lubricant to help prevent breakage and fit snugly so they don't slip off.

Secret #7Generic birth-control pills are not necessarily as good as name brands
Generic birth-control pills seem like an appealing option because they're less costly than their brand-name counterparts (as much as 60 percent less), but some experts say there isn't solid proof that they're as effective. "The FDA tests required for generics are far less rigorous than those required for the makers of brand-name drugs," explains Mitchell D. Creinin, M.D., director of family planning and family planning research at Magee-Womens Research Institute in Pittsburgh.
The FDA allows generic drugs to have a 20 percent plus or minus difference in blood-concentration levels when compared to the brand-name drug, according to the Association of Reproductive Health Professionals, meaning that the generic pills may be significantly less potent and still be approved for sale. So does this mean a higher risk of unplanned pregnancy for people who take generics? No one knows for sure. "When it comes to contraception, we shouldn't be guessing," says Dr. Harwood. "I have nothing against generics, but we're not talking about a headache, in which case if you take a pill and your headache doesn't go away, you can take another one. With the Pill, the only way to know it didn't work is if you get pregnant."
There's no question that having an unintended pregnancy is more expensive than paying a slightly higher cost for a brand-name contraceptive. But if you just can't part with the extra cash and choose to use generics, be extra vigilant about taking your Pill on time and consistently.

Birth-Control BasicsYou've probably heard this info before -- but better safe than sorry

You can get pregnant during your period. After sex, sperm can survive for up to five days inside a woman's body. So if you ovulate soon after you stop bleeding, you can conceive from having sex during menstruation.

The withdrawal method does not work. Withdrawal -- when a man pulls out of the vagina before ejaculating -- is incredibly risky because preejaculate fluid (which a man's penis can release at any point during intercourse) contains sperm. According to the Kaiser Family Foundation, a whopping 19 percent of couples who rely on withdrawal will conceive within a year.

Condoms can get stale. When reaching for a rubber, it's easy to forget to check the expiration date, but condoms that are past their prime can put you at risk for pregnancy and STDs because their material weakens over time.

Birth-Control FactsFACT: You can change your pill's start date by not finishing your placebo pills and beginning your next pill pack on the day you choose.FACT: Some birth-control methods are more likely to lead to an unplanned pregnancy in women who are of above-average weight.